Isocyanate terminated quasi-prepolymers useful for preparing polyurethane/polyisocyanurate foams having low thermal conductivity

Abstract

Polyurethane/polyisocyanurate rigid foams having low thermal conductivity are prepared from isocyanate-terminated quasi-prepolymers prepared from polyester polyols derived from phthalic anhydride or from the transesterification of polyethylene terephthalate scrap.

We claim: 
     
       1. An isocyanate-group terminated quasi-prepolymer consisting of the reaction product of an organic polyisocyanate with a polyester polyol consisting of the reaction product of phthalic anhydride and a low molecular weight aliphatic polyhydric alcohol. 
     
     
       2. The quasi-prepolymer of claim 1 wherein said organic polyisocyanate is selected from the group consisting of toluene diisocyanate, diphenylmethane diisocyanate, and polymeric MDI, and mixtures thereof. 
     
     
       3. The quasi-prepolymer of claim 2 wherein said organic polyisocyanate is polymeric MDI. 
     
     
       4. The quasi-prepolymer of claim 2 wherein said polyester polyol is utilized in an amount of from 2 to 30 percent by weight relative to the total quasi-prepolymer weight. 
     
     
       5. A polyisocyanurate foam prepared by the trimerization of the quasi-prepolymer of claim 4 in the presence of a trimerization catalyst, a blowing agent, auxiliaries and additives. 
     
     
       6. A polyisocyanurate foam prepared by the trimerization of the quasi-prepolymer of claim 4 in the presence of a trimerization catalyst, a blowing agent, auxiliaries and additives. 
     
     
       7. A urethane-group-containing polyisocyanurate foam prepared by the process comprising (a) reacting the quasi-prepolymer of claim 4 with   (b) a polyol selected from the group consisting of polyether polyols, hydroxyl-functional polyester polyols, and hydroxyl-functional polyesterether polyols; in an equivalent ratio of isocyanate groups to hydroxyl groups in excess of 1:1 in the presence of isocyanurate-group and urethane-group promoting catalysts, a non-reactive blowing agent, and suitable additives and auxiliaries.